Image forming method

Abstract

An objective is to provide an image forming method by which sufficient fixing strength can be obtained at a low temperature of 120° C., excellent print images with no belt-like or streak image defect can be obtained, and no document offsetting is generated even though the superimposed print images are stored. Disclosed is an image forming method comprising the step of fixing a toner image formed with a toner comprising a releasing agent on a transfer material employing a contact-heating fixing device comprising a heating roller and a belt-shaped pressure body, wherein the heating roller is placed on the upper side of the transfer material, the releasing agent comprises the 1 st releasing agent component and the 2 nd releasing agent component, and the 1 st releasing agent component has a content of 40-98% by weight, based on the total weight of the 1 st and 2 nd releasing agent components.

1. An image forming method comprising the step of:
 fixing a toner image formed with a toner comprising a releasing agent on a transfer material employing a contact-heating fixing device comprising a heating roller and a belt-shaped pressure body, 
 wherein the heating roller is placed on an unfixed toner image side of the transfer material; the belt-shaped pressure body is placed on a side opposite to the unfixed toner image side of the transfer material; a nip portion is formed with the heating roller and the belt-shaped pressure body; the belt-shaped pressure body having only two pressure pads to create the nip portion, where one of the two pressure pads is provided on an entrance side of the nip portion, and another one of the two pressure pads is provided on an exit side of the nip portion, a relationship between pressure X on the entrance side of the nip portion and pressure Y on the exit side of the nip portion satisfies X<Y; the releasing agent comprises a 1 st  releasing agent component containing a monoester compound represented by the following Formula (1) and a 2 nd  releasing agent component containing a hydrocarbon compound having a branched chain structure; and the 1 st  releasing agent component has a content of 40-98% by weight, based on the total weight of the 1 st  releasing agent component and the 2 nd  releasing agent component:
   R 1 —COO—R 2   Formula (1)
 
 
 
       wherein R 1  and R 2  each represent a hydrocarbon group with a main chain having 13-30 carbon atoms, that may have a substituent, or may not have a substituent, and R 1  and R 2  each may be identical or different. 
     
     
       2. The image forming method of  claim 1 ,
 wherein the 1 st  releasing agent component has a content of 70-95% by weight, based on the total weight of the 1 st  releasing agent component and the 2 nd  releasing agent component. 
 
     
     
       3. The image forming method of  claim 1 ,
 wherein tertiary carbon atoms and quaternary carbon atoms in the total carbon atoms constituting the hydrocarbon compound having a branched chain structure have a content of 0.1-20% by weight. 
 
     
     
       4. The image forming method of  claim 1 ,
 wherein tertiary carbon atoms and quaternary carbon atoms in the total carbon atoms constituting the hydrocarbon compound having a branched chain structure have a content of 0.3-1.0% by weight. 
 
     
     
       5. The image forming method of  claim 1 ,
 wherein the hydrocarbon compound having a branched chain structure is microcrystalline wax. 
 
     
     
       6. The image forming method of  claim 5 ,
 wherein the microcrystalline wax has 30-60 carbon atoms, a weight-average molecular weight of 500-800 and a melting point of 60-90° C. 
 
     
     
       7. The image forming method of  claim 1 ,
 wherein the nip portion formed with the heating roller and the belt-shaped pressure body has a width of 5-40 mm. 
 
     
     
       8. The image forming method of  claim 1 ,
 wherein the nip portion formed with the heating roller and the belt-shaped pressure body has a width of 10-30 mm. 
 
     
     
       9. The image forming method of  claim 1 ,
 wherein the belt-shaped pressure body is a seamless belt. 
 
     
     
       10. The image forming method of  claim 9 ,
 wherein the seamless belt is one having a layered structure formed from silicone rubber elastic layers and a PFA (perfluoroalkoxy) outer surface layer provided on a polyimide substrate. 
 
     
     
       11. The image forming method of  claim 9 ,
 wherein the seamless belt is one having a layered structure obtained by coating a releasing layer, in which a conductive material is added into a fluorine resin on a polyester substrate, a polyperfluoroalkyl vinyl ether substrate, a polyimide substrate or a polyetherimide substrate. 
 
     
     
       12. The image forming method of  claim 1 ,
 wherein the pressure X is 300-500 N and the pressure Y is 400-600 N, provided that X<Y.